1. Field of the Invention
The present invention relates to an ignition device for an internal combustion engine, more particularly to an ignition device of the alternating current (AC) continuous discharge type for controlling the primary coil current in an ignition coil.
2. Description of the Related Art
A conventional ignition device of the AC continuous discharge type has been disclosed, for example, in U.S. Pat. No. 4,356,807 (issued Nov. 2, 1982).
This conventional device can control the time of the discharge duration ranges of the ignition plug (spark plug) in one combustion stroke of the internal combustion engine. In this conventional device, an average discharge current range becomes more than 50 (mA), and thus this high average discharge current makes possible a so-called "high energy ignition" and can improve the ignition of the air/fuel mixture.
Nevertheless, a problem arises in this conventional device in that a peak voltage (6 to 8 (KV)), and then a direct current (DC) voltage (3 to 4 (KV)), are generated in a secondary coil, and both are supplied to the ignition plug when the primary coil current starts to flow. Because of these unnecessary voltages, the discharge of the ignition plug is started before the predetermined ignition timing, and thus a problem occurs in that the ignition timing becomes too advanced.